The first synthetic embryos developed ex utero reach the stage of organ growth

The first synthetic embryos developed ex utero reach the stage of organ growth

The first synthetic embryos developed ex utero reach the stage of organ growth

Jacob (Yaqub) Hanna, professor of molecular genetics, works on embryo samples in his laboratory at the Weizmann Institute of Science, August 4, 2022.

The black box is barely bigger than a wine case. The transparent upper part reveals a wheel that spins several tubes where tiny balls float in a yellowish liquid: these are embryos in full growth. The machine is a kind of artificial uterus that reproduces the conditions of gestation in the womb, invented by Professor Jacob Hanna and his team at the Weizmann Institute of Science in Rehovot, Israel. Last year they cultivated mouse embryos there, born from classical fertilization. Now they are growing “Synthetic embryos”, created from stem cells without gametes – the sex cells – or fertilization. The researchers managed to get them to develop for up to eight and a half days, a world first unveiled in early August.

A few days later, the review Nature published similar results, to which the Israeli team contributed, reflecting the effervescence and intense mix of competition and cooperation that has animated this field in recent years.

In both cases the turning point concerns both the method of obtaining and the duration of the culture: at this stage the embryos already have a developed brain, a beating heart, intestines, “somites”, which will give muscles, as well as a placenta. . They are 95% similar to natural mouse embryos at this stage of maturation, full gestation in the rodent is twenty days.

New horizons

The method can be transposed to man: the Israeli team has already grown “Synthetic embryos, at a very early stage”which are currently still very different from what nature produces, says Professor Jacob Hanna. Beyond the technical and scientific prowess, his study on the mouse, which aroused many fantasies after its publication in the journal Cell1uh August suggests new horizons, in particular to better understand the stages of embryonic development, and in the field of fertility or regenerative medicine.

Members of Professor Jacob Hanna's team at the Weizmann Institute of Science, Rehovot (Israel), 4 August 2022.

These “synthetic embryos” – synthetic embryosas they are called in Cell – they will not be able to carry out a complete gestation and become humans and mice, Professor Hanna points out from the beginning. He himself also hesitates on the proper term to designate them, because they are not made from a collection of cells, like other artificially obtained embryo models, but they are not natural for all of this. The 43-year-old scientist evokes ” embryos “, why they “They are far behind the embryos [issus d’une fécondation]. They can only grow in vitro for up to eight and a half days, compared to eleven days for embryos obtained by fertilization. This is the best, for now. Beyond, [on] I cannot[t] also call them embryos because they have so many malformations “. Only 0.5% of entities recreated in this way grow, a low success rate that doesn’t worry the team, because, at such an early stage, researchers can grow them en masse.

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